This invention relates generally to hand-held extruders for extruding polymeric materials and more particularly to a hand-held extruder adapted to extrude the polymeric materials at an improved predetermined rate and quantity. Additionally, the hand-held extruder in accordance with the present invention includes attachments which facilitate the handling and balancing of the extruder during use, and prevent the heated barrel from marring, damaging or otherwise injuring surfaces on which the extruder may be placed intentionally or accidentally.
The term "polymeric material" when used herein is intended to mean any polymer composition or mixtures of polymer compositions which can be heated to a consistency so that it can be extruded by suitable mechanical means such as a screw conveyor; for example; thermoplastic materials; elastomeric materials; and more particularly elastomeric sealant compositions; for which the present invention is particularly adapted.
The use of extruders for extruding elastomeric sealant materials is well known in the prior art as is shown in U.S. Pat. Nos. 2,668,986 and 3,953,006. Similarly, the use, of hand-held extruders is also well known in the art as is shown by U.S. Pat. Nos. 3,337,093, 3,750,905, 3,758,001, and 3,868,046.
In U.S. Pat. No. 3,750,905 one basic form of well known hand-held extruder easily purchasable on the open market used for the intermittent and continuous extrusion of heated thermoplastic sealant and other polymeric materials is shown as including, a generally unitary front assembly having, an elongated inner casing or barrel forming an extruding or feed passage extending end to end therethrough, and a three part outer housing consisting of, a barrel bushing, an insulated sleeve, and an end cap means so formed, shaped and connected that they hold and mount the elongated barrel therein, in fixed relative relation to the outer housing The feed passage has an inlet opening at one end which is in alignment in assembled position with an inlet port on the bushing barrel, open to the exterior of the hand-held extruder, so thermoplastic sealant or other polymeric material can be fed or introduced into the feed passage of the elongated barrel At the opposite end remote from the inlet opening a discharge outlet is in alignment with a discharge nozzle in the end cap so that heated thermoplastic sealant or other polymeric material can be dispensed from the hand-held extruder during the operation thereof Heating of the thermoplastic sealant or other plastic material charged into the feed passage is accomplished by means of electrical heating elements which are disposed along the longitudinal line of the barrel in suitable passages parallel to the feed passage along with a rheostat and a thermostat to control and maintain the barrel at a predetermined temperature depending on the conditions of operation. The thermoplastic sealant or other polymeric material is moved through the feed passage by means of a conventional screw type conveyor which is rotatably mounted in the feed passage for counterclockwise rotation and extends through a partition in the barrel bushing to enable the screw conveyor to be connected to suitable reduction gearing in a torque housing to which the barrel bushing can be detachably connected. The torque housing is in turn mounted in offset relation on the pistol grip section of a main housing for a suitable driving means such as an electric motor to which the opposite end of the reduction gearing is so connected that when the driving means is actuated during operation of the hand-held extruder by a trigger switch on the pistol grip main housing, the screw conveyor will be rotated in the desired counterclockwise direction to move the thermoplastic sealant or other polymeric material in the feed passage for dispensing the same from the dispensing nozzle in the end cap.
The hand-held extruder shown in U.S Pat. No. 3,750,905 discloses diagrammatically a complicated gear train for transmitting power from the electric motor to the screw conveyor It does not detail the actual elements in the drive train, but merely identifies them as being of conventional design. It will however be apparent to those skilled in the art from just the drawings that in order to convert the conventional clockwise direction of rotation of the electric motor to the counterclockwise direction of rotation for the conventional screw conveyor and to reduce the number of revolutions per minute at which the screw conveyor operates that a complex gear train; in actual commercial use epicyclic gearing was required; had to be used which entailed a large gear housing as shown in the drawing for U.S. Pat. No. '905.
This drive train caused problems because this hand-held extruder as disclosed in U.S. Pat. No. '905 operated relatively slowly, with a relative low efficiency, and barrel or other mechanical failures occurred because the viscosity of the material being extruded could not be controlled particularly during intermittent operation.
The present invention provides an improved hand-held extruder which overcomes these problems in which a modified air motor rotated in a counterclockwise direction is combined with a double or two-stage planetary reduction gear to provide a driving train to enable the extruder to discharge heated thermoplastic sealant or other polymeric materials at an improved rate and quantity without loss of torque or reduction of driving power during operation of the hand-held extruder.
Further, however, this driving train for the hand-held extruder in accordance with the present invention enables the generally unitary barrel assembly to be aligned with the gear train housing and the main housing which among other advantages prevents the mechanical failures heretofore experienced with the prior art form of extruder shown in U.S. Pat. No. '905, and enables the extruder in accordance with the present invention to operate within at least an 80% efficiency range.
The improved driving train and the corresponding changes in the construction which are achieved eliminated the complex gear train and offset gear box housing of the prior art extruder which absorbed horsepower due to friction thus reducing efficiency, and was one of the sources of mechanical failure. The offset gear box housing in the prior art extruder required special castings and thus increased the cost of manufacture of this prior art device.
The changes in the gear train for the hand-held extruder of the present invention permits alignment of the barrel assembly, the two stage planetary gear train housing and main housing for the air motor as is more fully described below, simplifies the construction, and reduces cost of manufacture and time of assembly during manufacture and in the field servicing of this improved hand-held extruder.
Thus, the driving train for the hand-held extruder in accordance with the present invention is stronger,.more dependable, reduces the down time of the extruder, and simplifies disassembly and reassembly in the field during commercial use of this device.
Additionally, the improved hand-held extruder in accordance with the present invention provides an improved handle assembly disposed in spaced relation to the pistol grip housing to enable the operator to better hold, grip, and balance the hand-held extruder during the use thereof.
The improved hand-held extruder in accordance with the present invention is also provided with a safety feature in the form of a tool or table rest about the generally unitary front assembly which prevents the marring or damaging of any adjacent surface on which the hand-held extruder may be placed accidentally, inadvertently or otherwise by the operator.